This could be the last season for 'Joan of Arcadia,' due to declining ratings. (CBS)

A religion-themed network drama faces cancellation if its ratings don't improve. "Joan of Arcadia," which airs Fridays at 8 p.m. ET on CBS, likely won't be renewed for a third season if its viewership doesn't spike as this TV season nears its end.

"Arcadia" features Amber Tamblyn as Joan, a high-school girl who receives visits from God in various guises like a lunch lady or cute guy. Joan had kept the visits a secret, but a recent storyline has had Joan reveal the visits to her boyfriend, Adam (Christopher Marquette).

The show debuted in 2003, carrying the mantle of faith and religion that "Touched by an Angel" held for nine seasons on CBS before calling it quits in 2003.

The freshman ratings for "Arcadia" were good enough to merit show's renewal. However, its ratings have dipped 26 percent in its sophomore run, according to Entertainment Weekly. The show is now averaging 8.1 million viewers.

"It's lost its appeal," an unnamed insider told EW. "It's no longer about Joan's dialogue with God and helping people." The publication did say, however, that "Arcadia" has something in its favor: CBS President Nina Tassler is a fan.

"Arcadia" began airing new episodes Apr. 1 after several weeks of repeats.

Presbyterians Today has covered the show since its inception. Contributor Teresa Blythe maintains a "Joan of Arcadia" page on the Web site, with mini-guides to discussing the show's episodes.

The page recently added a note about saving "Joan of Arcadia."

"This series is facing a bit of a ratings slump and is in danger of not being renewed for a third season," says the site. "If you enjoy this theologically-infused television series and don't want to see it canceled, the easiest thing to do is tune in on Friday nights to boost the ratings."

It also suggests writing CBS a letter supporting the show.

EW recently gave "Arcadia" four axes out of five, with five representing almost certain cancellation.

Other shows that might not be renewed because of poor ratings, according to EW, include "American Dreams" (NBC), "Arrested Development" (FOX), "The Bernie Mac Show" (FOX) and "Judging Amy" (CBS).